A data transmission method, a base station, and user equipment are provided. The method includes: receiving, by a base station, a random access request sent by user equipment, where the random access request carries indication information to request uplink scheduling information; and sending, by the base station, a random access response to the user equipment, where the random access response carries first uplink scheduling information or second uplink scheduling information, the first uplink scheduling information indicates that a message Msg 3 uses a first transport block, the second uplink scheduling information indicates that the Msg 3 uses a second transport block, the first transport block is larger than the second transport block, the first transport block can be used to transmit signaling and user data, and the second transport block can be used to transmit the signaling, but is not used to transmit the user data.